Activity and Stability of (Pr1-xNdx)(2)NiO4 as Cathodes for Solid Oxide Fuel Cells III. Crystal Structure, Electrical Properties, and Microstructural Analysis
This study is to complement an early article (Dogdibegovic et al., J. Electrochem. Soc., 163(13), F1344 (2016)) on the electrochemical activity and performance stability of (Pr1-xNdx)(2)NiO4+delta (PNNO) electrodes. Here, we report the crystal structure, electrical properties, and microstructures of PNNO series as the cathodes for solid oxide fuel cells. Rietveld refinements on powders (x = 0, 0.25, 0.50, 0.75, and 1) show that the unit cell volume decreases with an increase in x, primarily due to a decrease in the c lattice parameter. Larger cell volume (similar to 1.50%) and higher total electrical conduction (40%) in Pr2NiO4+delta are in favor with its mixed conducting properties during operation, but Pr2NiO4+delta cathode exhibits a severe phase evolution. Substitution of Pr with Nd shows the suppression of phase evolution in both thermally annealed powders and electrodes. An increase in Nd content leads to a full preservation of the parent phase in both (Pr0.25Nd0.75)(2)NiO4+delta and Nd2NiO4 after 2,500 hour annealing at elevated temperatures. Reaction with GDC buffer layer was also suppressed with the presence of Nd, which was shown by a reduction of Pr and Ni elemental diffusion into GDC bulk. STEM analysis confirms multiple phases present in an operated Pr2NiO4+delta electrode, while suppressed phase transition was observed in electrodes with high Nd content. (c) 2016 The Electrochemical Society
